Petri net extensions for the development of MIMO net models of automated manufacturing systems

In this paper, the development of multiple-input multiple-output (MIMO) subnets is discussed. Hierarchical time-extended Petri nets (H-EPNs), a form of extended Petri nets, allow the development of structured MIMO subnets to model complex system functionalities. In addition, H-EPNs also provide a means to convert such a MIMO structure to a single-input single-output (SISO) net that can easily be integrated within a top-down system decomposition. The activator arc definition is instrumental in deriving this transformation. The activator arc definition and the H-EPN subnet definitions are integrated with the SPNP (stochastic Petri net package) for simulation and analysis purposes. The activator arc extension allows a truly hybrid approach to Petri net (PN)-based systems modeling, analysis, and development of complex PN models of automated manufacturing systems. The case study emphasizes the usefulness of this extension in studying important issues such as static priority scheduling, dynamic failure recognition, and rescheduling in manufacturing systems. The SPNP package, suitably modified to handle the H-EPN extensions, is used for analysis and verification.